Master alloys containing rare earth metals



MASTER ALLOYS CONTAINING RARE EARTH METALS Wilbur T. Bolkcorn, AllisonPark, and William E. Knapp, Pittsburgh, Pa., assignors to AmericanMetallurgical Products (30., Pittsburgh, Pa., a partnership No Drawing.Application April 28, 1955, Serial No. 504,653

13 Claims. (Cl. 75-134) This invention relates to alloys andparticularly to an addition alloy for steel and the like metals wherebyrare earth metal may be more elfectively incorporated into the matrixmetal. The use of rare earth metals as an additive to metals matriceshas long been known. The use of the rare earth metals has, however, beensomewhat limited by reason of the relatively low efiicienoy uponaddition to the base or matrix material. Rare earth metals havegenerally been added to metal matrices in the form of individual purerare earth metals or in the form of mixtures such as Misch Metal whichis a mixture of rare earth metals in the proportions in which theynormally occur in ore bodies.

We have found that the effectiveness of the rare earth metals can bemarkedly increased by combining them with one or more metals of thegroup zirconium, titanium and hafnium in the form of an addition alloy.We have found that zirconium, titanium and hafnium may be admixed withthe rare earth metals in the following proportions:

Percent Rare earth metals 25 to 93 One or more of the group zirconium,titanium and hafnium 7 to 75 We have found that the rare earth metalsand one or more members of the group zirconium, titanium and hafnium inthe above proportions may be and preferably is admixed with a diluent toform an addition alloy which has a high density and other desirableproperties set out hereinafter. Preferably the diluent is a mixture ofmetals having a high density and a relatively low melting point. We havefound, for example, that manganese and nickel in the proportion of about1 /2 parts of manganese to 1 part nickel has a high density and a lowmelting point of about 1750 F. The diluent, however, may be iron,manganese, nickel, copper or similar metals either alone or incombination, to which are added a rare earth metal or rare earth metalmixture and one or more of the group zirconium, titanium and hafnium.Broadly, the addition alloy of our invention may have the followinggeneral composition:

Percent One or more of the group zirconium, titanium and hafnium 2 to 25Rare earth metal to 30 Diluent (preferably 1 /2 parts of manganese to 1part nickel) Balance Preferably, however, we limited the composition ofour addition alloy to a somewhat narrower range. The

preferred alloy has the following composition:

Percent One or more of the group zirconium, titanium and hafnium 2 to12.

Rare earth metal 10 to 30 Diluent (preferably 1 /2 parts of manganese to1 part nickel) Balance ited States Patent Patented Oct. 22, 1957 We havefound that the alloy of our invention gives a much greater efficiencythan the ordinary miseh metal of commerce, for example, in low alloysteel where the rare earth metals are added for improved impactproperties, approximately 1 lb. per ton of ordinary miseh metal wasrequired in order to achieve a minimum of 20 lbs. impact level on a Vnotch charpy test at minus 40 F. with a Brinell hardness of 500. Our newalloy of this invention consisting of 45% manganese, 30% nickel, 20%miseh metal and 5% zirconium, required a total alloy addition of 1 lb.per ton or only 0.2 lb. per ton of rare earth metal. In short, we areable to obtain an identical result with the use of only /5 as much rareearth metal as has been required in the past.

In stainless steel ordinary unprotected miseh metal gives a recovery ofonly approximately 50% of the rare earth elements, whereas the use ofthe present alloy permits recovery between to Several stainless steelheats using miseh metal in one series and the alloy of this invention(consisting of 45% manganese, 30% nickel, 20% miseh metal and 5%zirconium) in the other were prepared and the recovery or rare earthmetals determined. The results of this study are set out in Table 1herein below:

the titanium, zirconium or hafnium, as the case may be, appears to fluxout residual dirt which sometimes occurs when rare earth metals are usedin steel under unfavorable conditions and which has been a deterrent tothe use of rare earth metals.

The effectiveness of rare earth metal additions to a base steel isperhaps most strikingly illustrated by a comparison of V notch charpytests. A series of samples of a steel having 1.48% manganese, 28%carbon, 35% silicon, .0l5% sulphur, .Oll% phosphorus, .63% chromium, 58%molybdenum, .11% nickel and 002% boron were tested both with theaddition of our new alloy, standard rare earth miseh metal, and withoutthe addition of any We have found that the addition alloy of the presentinvention can be made most successfully by incorporating the titanium,zirconium or hafnium in the form of relatively pure metal such as spongemetal or scrap rather than in the form of their ferro alloys. We havefound that the usual ferro titanium, ferro zirconium ornickelsilicon-titanium or nickel-silicon-zirconium form high meltingintermetallic components when added to the rare earth metals, so thatthe recovery is relatively low and is extremely variable. For thisreason and other reasons which are apparent from the foregoingdisclosure the separate addition of rare earth metals and alloys ofzirconium,'titanium or hafnium to the molten bath will not produce theunusual advantages characteristic of the addition alloy of ourinvention.

When we speak of rare earth metals in this application we have referenceto that group of metals having atomic members between 58 and 71 of theperiodic table. Misch metal is the term comm-only used in the industryfor a mixture of rare earth metals produced by reduction from naturallyoccurring rare earth ores and contains an admixture of various rareearth metals in the approximate proportions in which they occur in theore. The most common rare earth metals are cerium, lanthanum, neodymiumand praseodymium and these metals are the principal constituents ofmisch metal.

We have set out certain preferred compositions of our alloy and havedescribed a preferred method of making the same. It will be understood,however, that the alloy of this invention may be otherwise made andembodied within the scope of the following claims.

We claim:

1. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of a mixture of about 25% to 93% rare earthmetals and about 7% to 75% of one or more metals selected from the groupzirconium, titanium and hafnium all incorporated in a suflicient amountof metal diluent of high density compatible with the metal bath to forma mixture whose density is greater than the bath. 2. An addition alloyfor incorporating rare earth metals into a metal bath consistingessentially of a mix- .ture of about 45% to 93% rare earth metals andabout 7% to 55% of one or more metals selected from 'the groupzirconium, titanium and hafnium allincorporated in a sufiicient amountof metal diluent of high density compatible with the metal bath to forma mixture whose density is greater than the bath.

3. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 10% to 30% rare earth metals, about2% to of one or more metals selected from the group zirconium, titaniumand hafnium and the balance a metal diluent of high density compatiblewith the metal bath.

4. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 10% to 30% rare earth metals, about2% to 10% of one or w into a metal bath consisting essentially of about10% to 30% rare earth metals, about 2% to 25 of one or more metalsselected from the group zirconium, titanium and hafnium and the balancea metal diluent selected from the group manganese, nickel, copper andiron and mixtures thereof.

6. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 10% to 30% rare earth metals, about2% to 10% of one or more metals selected from the group zirconium,titanium and hafnium and the balance a metal diluent selected from thegroup manganese, nickel, copper and iron and mixtures thereof.

7. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 10% to 30% rare earth metals, about2% to 25% of one or more metals selected from the group zirconium,titanium and hafnium and the balance made up of manganese and nickel inthe proportions of 1 /2 parts of manganese to 1 part of nickel.

8. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 10% to 30% rare earth metals, about2% to 12% of one or more metals selected from the group zirconium,titanium and hafnium and the balance made up of manganese and nickel inthe proportions of about 1 /2 parts of manganese to 1 part of nickel.

9. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 20% misch metal, 5% zirconium, 30%nickel and 45% manganese.

10. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 20% misch metal, 5% titanium, 30%nickel and 45% manganese.

11. The method of adding rare earth metals to a metal bath comprisingthe steps of forming a molten bath of the metal to be treated, adding tothe bath an alloy consisting essentially of about 25% to 93% rare earthmetals and about 7% to of one or more metals selected from the groupzirconium, titanium and hafnium.

12. The method of adding rare earth metals to a metal bath comprisingthe steps of forming a molten bath of thev metal to be treated, addingto the bath an admixture consisting essentially of about 10% to 30% rareearth metals, about 2% to 25% of one or more metals selected from thegroup zirconium, titanium and hafnium and the balance metal diluent ofhigh density compatible with the metal bath.

13. An addition alloy for incorporating rare earth metals into a metalbath consisting essentially of about 10% to 30% rare earth metals, about2% to 25 of one or more metals seletced from the group zirconium,titanium and hafnium and the balance iron.

References Cited in the file of this patent UNITED STATES PATENTS1,023,208 Lesmuller Apr. 16, 1912 2,642,358 Kent June 16, 1953 FOREIGNPATENTS 488,322 Great Britain July 5, 1938 498,599 Belgium Feb. 1, 1951

4. AN ADDITION ALLOY FOR INCORPORATING RARE EARTH METALS INTO A METALBATH CONSISTING ESSENTIALLY OF ABOUT 10% TO 30% RARE EARTH METALS, ABOUT2% TO 10% OF ONE OR MORE METALS SELECTED FROM THE GROUP ZIRCONIUM.TITANIUM AND HAFNIUM AND THE BALANCE A METAL DILUENT OF HIGH DENSITYCOMPATIBLE WITH THE METAL BATH